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Author Topic: Any hope of faster sensors?  (Read 6715 times)

Jack Flesher

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Any hope of faster sensors?
« Reply #20 on: October 15, 2009, 11:52:55 am »

Quote from: bjanes
You seem to be confusing total noise with thermal noise.

Nope -- I think you'll find that thermal noise makes up the greater part of ISO noise whether it is amplified after the fact or generated on-chip during capture...  We all know you are the most brilliant person sharing photographic knowledge on the internet and so I defer to your supreme intellect in these matters... But I ask you again, can you please point us to ANY consumer CCD camera that outperforms a current consumer CMOS camera on ISO noise?  
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BJL

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« Reply #21 on: October 15, 2009, 12:36:08 pm »

Quote from: Jack Flesher
I think you'll find that thermal noise makes up the greater part of ISO noise whether it is amplified after the fact or generated on-chip during capture.
Do you have any source for that? I asked Eric Fossum, inventor of the modern active pixel type of CMOS sensor and still working in the CMOS sensor industry, in a DPReview forum discussion, and he confirmed that to the best of his knowledge (vastly greater than yours or mine) thermal noise from within photosites is not a significant factor, as it is greatly overshadowed by amplifier noise. (Except in long exposures, when dark current noise accumulation can be an issue.)

Also, as soon as the illumination of a pixel is half-way decent, about 100 photons or more detected, photon shot noise overwhelms both read noise (mostly amp. noise) and thermal noise.

Quote from: Jack Flesher
can you please point us to ANY consumer CCD camera that outperforms a current consumer CMOS camera on ISO noise?
I do not see the point of that question since no-one is disagreeing that modern CMOS sensors outperform CCDs at high ISO. The only disagreement is about the reasons for that advantage. My answer: mostly a better approach to amplification allowed by the active pixel approach of modern CMOS sensors vs the passive pixels of CCDs. By the way, once upon a time there were "passive pixel" CMOS sensors, but they were only useful as a cheap but noisy low end alternative to CCD's.
« Last Edit: October 15, 2009, 01:13:20 pm by BJL »
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bjanes

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Any hope of faster sensors?
« Reply #22 on: October 15, 2009, 12:55:32 pm »

Quote from: Jack Flesher
Nope -- I think you'll find that thermal noise makes up the greater part of ISO noise whether it is amplified after the fact or generated on-chip during capture...  We all know you are the most brilliant person sharing photographic knowledge on the internet and so I defer to your supreme intellect in these matters... But I ask you again, can you please point us to ANY consumer CCD camera that outperforms a current consumer CMOS camera on ISO noise?

Jack,

I thought that you had given up on this point . You seem to have edited your response and invented a new type of noise: ISO Noise. Noise at high ISO comes from the same sources as noise at low ISO and the main components (exclusive of PRNU) are shot noise and read noise. Thermal noise is negligible at exposures of less than a second. If you had taken the trouble to read the essays by Roger Clark or Emil Martinec (both of whom are PhDs in astrophysics and physics), you would know that thermal noise is not significant under normal photographic conditons.

In his analysis of the Canon 1D MII, Roger Clark found that average dark currents (thermal noise) were 0.013 to 0.02 electrons/second, but some pixels had dark currents as high as about 0.25 electrons/second. With an exposure of 1 second, 0.25 electrons is insignificant, when compared to total noise, but does become significant with exposures of 623 and 1800 seconds (see Equation 2). The read noise of this camera at an ISO of 3200 is 3.93 electrons and about 1650 electrons are collected at maximum signal (Table 1b). The shot noise for 1650 electrons is sqrt (1650) = 41 electrons. The thermal noise is 0.25 electrons at maximum. The total noise at maximum signal is sqrt (41^2 + 3.93^2 + 0.25^2) = 40.81. With the lens cap on, noise would consist almost entirely of read noise, since there would be no shot noise and this would determine the engineering definition of dynamic range. Figure it out.

Now you are specifying consumer grade cameras and a new kind of noise. What you are asking is irrelevant to the discussion and is pure obfuscation. Your sarcasm only shows what a poor looser you are. Give it up!

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ThierryH

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Any hope of faster sensors?
« Reply #23 on: October 15, 2009, 02:22:19 pm »

Quote from: bjanes
Now you are specifying consumer grade cameras and a new kind of noise. What you are asking is irrelevant to the discussion and is pure obfuscation. Your sarcasm only shows what a poor looser you are. Give it up!

bjanes,

If I were you, I would give up, with Jack (or Guy), you won't win and he (they) will always find a way to get away, by either editing or changing the subject in a way to present it at his (their) advantage: I have made the experience many many times, here and elsewhere.

I know this post and words will get me again a harsh response, but I don't care, he (they) knows what I am thinking about him (them).

All the best,
Thierry
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Jack Flesher

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Any hope of faster sensors?
« Reply #24 on: October 15, 2009, 03:46:04 pm »

Quote from: BJL
no-one is disagreeing that modern CMOS sensors outperform CCDs at high ISO.

I obviously read certain responses differently than you did...  But assuming you're right, then we're all in agreement on the main point which is, "CMOS sensors outperform CCDs at high ISO."

Cheers,

 


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bjanes

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« Reply #25 on: October 15, 2009, 04:48:43 pm »

Quote from: Ray
In fact, in the preview of the D3s by Marcus Bell, linked on 'What's New', Marcus claims that ISO 12,800 seems equal to the old D3 at ISO 3200.

I'm very skeptical. I'm reminded of the hype that surrounded the introduction of the D3. It was claimed to have (up to) 2 stops better high-ISO performance than any other DSLR on the market. In fact, my own tests indicated fairly conclusively the D3 had at most 1/2 a stop lower noise than the old 5D.

What was happening is that D3 jpegs were subject to greater in-camera chroma noise reduction than 5D jpegs and therefore looked much cleaner but were also softer than the 5D images. After applying a suitable amount of chroma noise reduction to the 5D image with Noise Ninja, there was very little image quality advantage to the D3 at ISO 3200 and above, on average about 1/3rd of a stop. D3 RAW images after processing and equal amounts of noise reduction also showed no more than 1/2 a stop improvement over the 5D.

Ray,

You are right to be skeptical of unsubstantiated claims of people wishing to diss other than their favorite camera brand, but the DXO ratings which you quote gave the Canon 5D, Canon 1DMII and D3 high ISO ratings of 1368, 1003, and 2250 respectively. The D3 was the first Nikon camera to best Canon in that area, but likely Canon will leapfrog Nikon in the near future. In any case my D3 and your Canon will continue to do the jobs for which we purchased them in the first place. Everyone wins from healthy competition.

Bill
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bjanes

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Any hope of faster sensors?
« Reply #26 on: October 15, 2009, 04:52:30 pm »

Quote from: Jack Flesher
I obviously read certain responses differently than you did...  But assuming you're right, then we're all in agreement on the main point which is, "CMOS sensors outperform CCDs at high ISO."

Cheers,

Jack,

We all know that you are a great photographer with bags of expensive high end medium format digital cameras, but now the question is can you read beyond an 8th grade level?

Cheers,

Bill
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